nix/doc/manual/rl-next/store-object-info.md

synopsis	prs
Store object info JSON format now uses `null` rather than omitting fields.	9995

The store object info JSON format, used for e.g. nix path-info, no longer omits fields to indicate absent information, but instead includes the fields with a null value. For example, "ca": null is used to to indicate a store object that isn't content-addressed rather than omitting the ca field entirely. This makes records of this sort more self-describing, and easier to consume programmatically.

We will follow this design principle going forward; the JSON guidelines in the contributing section have been updated accordingly.